In optical communication or wireless communication, digital signals are transmitted and received. In many cases, a digital signal receiving device compensates for waveform distortion of the digital signal using a digital filter (for example, see Patent Document 1 and Non-patent Document 1).
Patent Document 2 discloses the following technique. First, Fourier transform is performed on a digital signal. Then, a waveform equalization process in a frequency domain is performed on the Fourier-transformed signal by a digital filter. Then, inverse Fourier transform is performed on the result of the waveform equalization process to generate a digital signal.
Non-patent Document 2 discloses a method which switches filter coefficients in a semi-fixed manner using a lookup table (LUT) to control a frequency-domain equalization (FDE) circuit that is difficult to control, thereby performing wavelength dispersion compensation.